【 Application 】 Use MS20 stability analyzer to measure the average particle size of dispersed system particles

【Project Summary】

Tiny particulate matter has a wide range of applications in daily life and industrial production. The size and distribution of particles directly affect industrial processes, product quality, energy consumption, and production safety. Therefore, accurate and convenient measurement of the particle size of small particles is very important. The measurement of particle size can serve various application fields such as cosmetics, chemistry, pharmaceuticals, or food.

Represented by Beijing Odrino Instrument Co., Ltd., GermanyDefeiThe MS20 (Figure 1) produced by Data Physics Instrument Company is a comprehensive characterization instrument based on the principle of multiple light scattering to evaluate the stability of multiple dispersed systems and the instability mechanisms related to time and temperature. It provides a simple and fast method to measure the average particle size of particles in a dispersed system. This article will introduce the use of MS20 stability analyzer to measure the average particle size of two types of polystyrene particles.

[Image]1]MS 20 Stability Analyzer

Measurement principle:

The MS20 stability analyzer is based on the principle of multiple light scattering. A beam of light is absorbed into a liquid sample, and suspended particles in the sample cause multiple scattering of the light entering the sample (scattering in all directions away from the incident direction). This phenomenon is called multiple light scattering. After entering the sample, the incident light is continuously scattered multiple times, and the intensity of the light emitted from the sample depends on the wavelength of the light, particle concentration, particle size, refractive index of continuous and dispersed phases, and absorption coefficient. Multi light scattering technology can detect the stability of dispersed systems, including changes in particle size over time, particle migration speed, stability index, etc. This instrument is suitable for dispersed systems such as solid/liquid, liquid/liquid, gas/liquid, etc.

According to the Stokes formula and the migration rate V calculated through MS20 measurement, the average particle size can be calculated𝑑:

among which, Δ𝜌It is the density difference between particles and liquids;

𝑔It is the acceleration due to gravity, approximately 9.81 meters/s2；

𝜂It is the viscosity of the liquid.

Experimental process:

This experiment used two types of polystyrene particles with different particle sizes (PS1 and PS2) (Figure 2). The particle sizes of PS1 and PS2 particles given on the packaging are 20 µ m and 40 µ m, respectively. The solvent of the suspension is water, and its density and viscosity are 0.998g/cm3 and 1.002mPas, respectively, at room temperature. The volume fraction is 5%.

[Image]2]

Prepare it20mlPour the polystyrene suspension into the sample tube and set the experimental conditions to25°CBelow each1Measure every minute, continuously measure1Hour. The measurement area is0mm(Bottom of sample tube) and56.5mmBetween the top of the sample tube.

(Image)3）Two measurement results of polystyrene suspensions were provided.

* among whichTransmissionRepresents transmitted light,BackScatteringRepresenting backscattered light;

*The horizontal axis is from left toRight representativeSample tube from bottom (position)0mm ）To the top (position)56.5mm ）；

*The color code of the curve represents the time of measurement, starting from red (the first measurement,t=0s）To purple (last measurement,t=1h）. Each curve represents a separate measurement value.

image3Transmission map and backscattering inClear pictureThe ground displays the time-dependent and position dependent changes of light intensity, reflecting a typical subsidence process. It can be seen that due toPS1The particle size is small and the settling rate is slow，PS1The ratio of changes in transmitted and backscattered light intensityPS2Much slower.

[Figure 4] Calculation of average migration rate and average particle size of particles in PS1 suspension

利用MS20The corresponding functions in the software can easily calculate the migration rate of two types of sample particles, as shown in the figure4As shown,PS1The average migration rate of particles in the suspension is0.6262 mm/min(Image)4On the left side. According to the Stokes' law calculation function in the software, input the corresponding parameters such as volume fraction, and simply click on "Calculate" in the software to obtainPS1The average particle size (Figure)4On the right side)19.88umSimilarly, calculatePS2The average particle size is39.54um(Table)1）.

(Table)1）

Conclusion:

passMS20measuredPS1 and PS2 averageThe particle sizes are19.55µmand39.54µmThe measurement results of the two samples are almost consistent with the values provided by the manufacturer, which confirms the use ofMS20Measuring the average particle size is accurate and reliable.

useMS20stability analysisInstrument and itsThe multifunctional software equipped can efficiently and accurately measure the average particle size of the sample. Apart from thisMS20It also has the ability to measure samplesoneThe functions of measuring sample layer thickness over time, calculating stability index, and analyzing the instability mechanism of dispersed systems can be widely applied in various fields such as fine chemicals, food, medicine, pesticides, petroleum, and new energy.

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